1. Field of the Invention
The present invention relates to a mobile crane. More particularly, the present invention relates to a structural configuration of a mobile crane""s chassis, a tag axle assembly, and an outrigger, which allows the mobile crane to be selectively variably configured for operation and selectively variably configured for road travel.
2. Description of the Relevant Art
In the past, a manufacturer of mobile cranes had to design at least two configurations of a mobile crane in order to better serve a world market. For example, FIG. 1 illustrates a mobile crane 2 designed taking into consideration certain factors pertinent to the United States market, whereas, FIG. 2 illustrates a mobile crane 4 designed for the European market.
The mobile crane 2 of FIG. 1 has a plurality of weight bearing axles 6, which are spaced relatively far apart, and a removable rear outrigger 8. Prior to travel on a U.S. road, the removable rear outrigger 8 is removed, and can be transported by a separate vehicle. Removing the rear outrigger 8 reduces the overall weight of the mobile crane 2. A middle outrigger 10 may be fixed, or removable, depending upon whether a further weight reduction is required in order to meet maximum weight restrictions for road travel.
The axles 6 are spaced relatively far apart in order to meet axle spacing requirements set by federal, state or local bridge weight regulations. For example, the minimum wheel spacing requirement in some areas is 18 feet, measured from the first axle in the first axle group to the first axle in the second axle group.
The mobile crane 2 is particularly well suited for the U.S. market because it can be driven to and from most job sites without requiring special permits or waivers of the maximum weight or minimum axle spacing requirements for road travel. The larger spacing between axles 6 and the larger overall length of the mobile crane 2, while enabling the mobile crane 2 to meet road travel restrictions, somewhat limit the maneuverability of the mobile crane 2 on narrow and/or curvy roads. However, because U.S. roads are typically designed with minimal curvatures and are usually relatively wide, the larger axle spacing and overall length still allows the mobile crane 2 to be safely driven to job sites.
The mobile crane 4 of FIG. 2 has a plurality of weight bearing axles 12, which are spaced relatively close, and a fixed rear outrigger 14 and fixed middle outrigger 16. The other structural features of the mobile crane 4 are similar or identical to the other structural features of the mobile crane 2.
The mobile crane 4 is particularly well suited for the European market. European roads are often narrow with tight curves. Therefore, closer axle spacing and a shorter overall length is desired in order to maneuver the mobile crane 4 to and from a job site. There are usually no axle spacing requirements for bridge travel, which facilitates shorter overall lengths. Further, in European countries, the maximum axle weight requirements are usually set much higher than the U.S. requirements. For example, mobile cranes driven in Europe typically have axle weights up to 12 metric tons. This often makes it more feasible to have fixed outriggers on the crane chassis. Of course, the rear outrigger 14 or middle outrigger 16 could be removable if needed, in order to meet the European maximum axle weight requirements.
When a manufacturer of mobile cranes attempts to design a new mobile crane for the world market, a problem arises. If the crane manufacturer offers a mobile crane with a U.S. oriented carrier or chassis, sales of the mobile crane in Europe will suffer due to poor mobility on European roads. If the crane manufacturer offers a mobile crane with a European oriented carrier or chassis, sales in the U.S. will suffer due to a frequent need to obtain special permits and waivers in order to drive the mobile crane on U.S. roads. Therefore, it has been necessary for a worldwide crane manufacturer to undertake the costly and time consuming task of designing, testing and building two different crane carriers for a single crane model, one chassis for the U.S. market and one chassis for the European market.
It is an object of the present invention to eliminate the cost and time required in designing, testing and/or building two carriers or chassises for a single crane design, while still providing a crane to serve a worldwide market.
It is an object of the present invention to provide a chassis structure which can be easily converted or reconfigured for use in the U.S. market, European market, or other markets.
These and other objects are accomplished by a mobile crane assembly comprising: a chassis; first connection features located on a portion of said chassis; an outrigger including at least one ground engaging portion for engaging the ground when said mobile crane is stationary; second connection features located on said outrigger for mating with said first connection features of said chassis to removably attach said outrigger to said portion of said chassis; a tag axle assembly including at least one wheel for rolling along a ground surface; and third connection features located on said tag axle assembly for mating with said first connection features of said chassis to removably attach said tag axle assembly to said portion of said chassis, wherein said first connection features may accept either said second connection features or said third connection features, such that said mobile crane can be connected to either said outrigger or said tag axle assembly, respectively.
Further, these and other objects are accomplished by a method of operating a mobile crane comprising the steps of providing a mobile crane including a chassis with first connection features located on a portion of the chassis; an outrigger having second connection features being attached to said first connection features; and a tag axle assembly having third connection features; detaching the second connection features from the first connection features to remove the outrigger from the portion of the chassis; attaching the third connection features to the first connection features to attach the tag axle assembly to the portion of the chassis; engaging at least two wheels of the tag axle assembly with a ground surface; and moving the mobile crane.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.